I. Field of the Invention
This invention relates generally to a machine for facilitating removal and replacement of tires on the rims of motor vehicles, and more particularly to a machine of the type described which is capable of accommodating a wide variety of sizes of tire rims and which includes an improved system for clamping and rotating the tire during the removal and replacement of a tire relative to its rim.
II. Discussion of the Prior Art
In the 1930's and early 1940's no machines had been devised for facilitating the changing of flat tires. Removal of an inflatable rubber tire from the wheel rim was totally a manual process involving the use of a series of pry bars called tire irons. Generally speaking, an uninflated wheel would be laid on the ground and an attempt would be made to break the bead free from the rim by first standing on the side wall and bringing as much force to bear as possible by jumping. Once the beads were broken loose from the rim, the repair person would pry the rubber tire free of the rim by inching along the periphery with a series of pry bars. The steps would be repeated when the new tire casing was being reinstalled.
In the late 1940's or early 1950's, some improvement had been made in the technology for facilitating the changing of vehicle tires and repairing flat tires. For example, the Nelson U.S. Pat. No. 3,142,330 discloses a hydraulically actuated bead breaker in which a shoe on the lower end of an arm is hydraulically actuated through a cylinder and a lever to apply a sufficient force for unseating the tire bead from the rim. The Strang et al U.S. Pat. No. 3,493,030, the Held U.S. Pat. No. 3,522,832 and the Schultz et al U.S. Pat. No. 3,780,785 each describe tire changing apparatus utilizing a rotatable horizontal table to which the wheel may be clamped. To achieve clamping, however, a conical chuck screwing onto a centrally disposed post passing through a central circular opening in the wheel rim is used to hold the tire onto the turntable. Such a machine is of limited current value, given the fact that many automotive wheels no longer have a central opening formed therethrough with which the prior art conical chuck can be made to cooperate. Then, too, in connection with those prior art machines, a series of manual operations were necessary to fit the clamping chuck in place and to screw it down to its clamping position. This necessarily made the clamping operation cumbersome and significantly more time-consuming.
The machine of the present invention obviates many of the drawbacks of the prior art identified above. In particular, the clamping arrangement for securing a tire to a turntable has been significantly improved so that the mere actuation of a hydraulic circuit will bring the clamping mechanism into play. Secondly, the clamping mechanism is not dependent upon the presence of a central opening in the tire's wheel rim, but instead, grips the rim in one or the other of two locations whereby tires of different sizes can be accommodated.